Topic: Tephigram

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A tephigram is one of four thermodynamic diagrams commonly used in weather analysis and forecasting.

The tephigram was invented by Napier Shaw in 1915 and is used primarily in the United Kingdom and Canada.

The principal reason that tephigrams are used by the British Met Office is the property that areas contained by the curves have equal energies for equal areas, leading to better comparisons of CAPE and hence convective systems.

On the tephigram you will see myriads of criss-crossing lines - they will be explained, but all this diagram really is telling us what the conditions are like from the surface to the upper atmosphere.

It is the reverse of the process of a parcel of air rising, expanding and cooling - a parcel of air brought to the surface from higher in the atmosphere, will compress and the temperature will increase at 10°C per 1000m as it descends.

The tephigram in the first figure, shows a moist layer and a dry layer - where the two dark lines are closer together, the more moist the atmosphere, the further apart, the drier the atmosphere.

If you move in the tephigram, go left along the isobar to symbolize no pressure change, where the correct mixing ratio line crosses that isobar, the isotherm at that intersection gives the dew pointtemperature.

On the tephigram, go straight up the dry adiabat until reaching the mixing ratio line and record the temperature isotherm there.

Go up or down the correct adiabat on a tephigram until reaching the 1000 isobar and read the temperature.

On the completed tephigram the area between the plot for environment temperature profile and the plot for the rising parcel temperature profile is directly related to the CAPE, which in turn is directly related to the maximum vertical speed in a Cb updraught.

A tephigram is a thermodynamic graph used by meteorologists for plotting atmospheric temperature and moisture profiles.

The observed temperature profile is in the centre and the expected rising parcel temperature profile is to the right of it with the amount of CAPE related to the area between the plots.

On the tephigram you will see myriads of criss-crossing lines - they will be explained, but all this diagram really is telling us what the conditions are like from the surface to the upper atmosphere.

It is the reverse of the process of a parcel of air rising, expanding and cooling - a parcel of air brought to the surface from higher in the atmosphere, will compress and the temperature will increase at 10°C per 1000m as it descends.

The tephigram in the first figure, shows a moist layer and a dry layer - where the two dark lines are closer together, the more moist the atmosphere, the further apart, the drier the atmosphere.

The last question is to be partly completed on a tephigram, to be handed in with your answers.

Visualizing an entrainment event and the ensuing downdraft on a tephigram.

(graphical, using a tephi, please hand in the analyzed tephigram) Use the parcel technique to plot the variation of temperature and dewpoint, both for the undiluted parcel and the environment, between the ground and 600 mb, on an aerological diagram (hand-out).

An IOP only occurred if it was thought that the weather conditions looked favourable for convective activity; this was decided by a team of experienced meteorologists and the Met office forecast model.

CAPE is the buoyancy of an air parcel vertically integrated between the level of free convection (LFC) and the level of neutral buoyancy (LNB) at which the parcel ceases to have virtual potential temperature of the environment and thus decelerates vertically.

It could be correctly argued that this puts a lot of faith in the model used to produce the tephigram, however, other parameters were also analysed including satellite and radar imagery.